Remove the concept of user stylesheets.

Source/web/WebDocument.cpp

Index: Source/web/WebDocument.cpp
diff --git a/Source/web/WebDocument.cpp b/Source/web/WebDocument.cpp
index e34072b04327fb5c92670a56d37865f28a7d48f9..7bdc58413a90b5f18993c60dbe50e62f572856ae 100644
--- a/Source/web/WebDocument.cpp
+++ b/Source/web/WebDocument.cpp
@@ -206,17 +206,18 @@ WebDocumentType WebDocument::doctype() const
     return WebDocumentType(constUnwrap<Document>()->doctype());
 }
 
-void WebDocument::insertUserStyleSheet(const WebString& sourceCode, UserStyleLevel styleLevel)
+void WebDocument::insertUserStyleSheet(const WebString& sourceCode, UserStyleLevel)
+{
+    insertStyleSheet(sourceCode);
+}
+
+void WebDocument::insertStyleSheet(const WebString& sourceCode)
 {
     RefPtr<Document> document = unwrap<Document>();
     ASSERT(document);
     RefPtr<StyleSheetContents> parsedSheet = StyleSheetContents::create(*document.get());
-    parsedSheet->setIsUserStyleSheet(styleLevel == UserStyleUserLevel);
     parsedSheet->parseString(sourceCode);
-    if (parsedSheet->isUserStyleSheet())
-        document->styleEngine()->addUserSheet(parsedSheet);
-    else
-        document->styleEngine()->addAuthorSheet(parsedSheet);
+    document->styleEngine()->addAuthorSheet(parsedSheet);
 }
 
 void WebDocument::watchCSSSelectors(const WebVector<WebString>& webSelectors)